Witness mark question

I finally got around to following the sage advice of putting witness marks on the Y stepper gears and noticed that mine don’t look like the usual pictures I have seen. The shaft is recessed into the center of the gear such that you can’t really mark it easily.

I have the Pro XXL. Is this normal? Are mine misaligned? I don’t have much room left on the side rails to shift that belt.

This is the right sided the left is slightly better but still recessed.

There is nothing wrong. The stepper motors only have a fixed length shaft. The SO4 machines increased the belt width but use the same stepper motors they use. So just reach in with a fine line sharpie and mark your shaft.


What does marking the shaft do? Where do you mark it exactly?

Putting a “Witness Mark” on the shaft and pully allow one to see if the pulley shifts on the shaft.

I like to align the mark w/ the pulley set screws, but that’s not necessary.

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I may have more room to actually mark the edge of the shat than the end. I may try that.

On my setup with the shaft to the end of the pulley I can do a one-second check to see if it is walking or spinning on the shaft.

As Will mentioned, If it had been aligned with the flat on the shaft, it would have been better.


More difficult with the recessed shaft but I will find a way.

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